Mass Mill Widowbloom

With the combined data of over 100.000 herbs, these are the milling results:

Results are per 100 herbs:
19,6 Umbral pigment 9,9 Luminous pigment 0,5 Tranquil pigment - Marrowroot
19,4 Umbral pigment 9,6 Luminous pigment 0,5 Tranquil pigment - Widowbloom
9,9 Umbral pigment 19,4 Luminous pigment 0,5 Tranquil pigment - Rising Glory
9,7 Umbral pigment 20,5 Luminous pigment 0,4 Tranquil pigment - Vigil's Torch
14,4 Umbral pigment 14,7 Luminous pigment 0,5 Tranquil pigment - Death Blossom
26,3 Umbral pigment 23,2 Luminous pigment 30,5 Tranquil pigment - Nightshade

As we round these numbers up it's easy to see Death Blossom gives about equal amounts of Umbrals and Luminous.
Marrowroot and Widowbloom give twice as many Umbrals as Luminous.
Rising Glory and Vigil's Torch give twice the amount of Luminous as Umbrals.

This can be gotten from all 6 shadowland herbs. Death Blossom Marrowroot Rising Glory Vigil's Torch Widowbloom Nightshade

From beta milling, while each herb does have a different ratio (based on current small data), its safe to assume that the first 5 herbs produce similar milling values. More data further down the line may change that.

4.8k of the the first 5 herbs, or 240 mills. This doesnt include Nightshade:
689 Umbral Pigment 14.35%
711 Luminous Pigment 14.81%
34 Tranquil Pigment 0.71%

700 Nightshade or 35 Mills:
192 Umbral Pigment 27.43%
165 Luminous Pigment 23.57%
213 Tranquil Pigment 30.43%

% values are per herb. So 100 Nightshades = 27 Umbral, 23 Luminous pigments and 30 tranquil pigment on average.